1. Field of the Invention
The present invention relates to a sheet post-processing apparatus, and, more particularly to a sheet post-processing apparatus with improved stacking properties for discharged sheets.
2. Description of the Related Art
A sheet post-processing apparatus is used in order to receive sheets from an image forming apparatus and apply post-processing such as stapling, punching, and sorting to the sheets. In performing these kinds of processing, when the sheets are discharged from a processing tray for stacking the sheets to a sheet discharge tray for stacking the sheets after the processing, a leading end of a sheet discharged may hang down and push out sheets already stacked in the sheet discharge tray. This occurs, in particular, in a model that lifts a sheet discharge tray when sheets are discharged.
Concerning this problem, there is proposed a technique for providing, in a discharge port, plural rollers that drive in a pair and providing a guide unit that flips up an end of a sheet parallel to a conveying direction of the sheet, sending the sheet through the rollers formed in a pair to discharge the sheet while curving the sheet (e.g., JP-A-8-133549).
However, in this technique, when plural sheets are discharged, an interval of the rollers has to be adjusted according to the thickness of the sheets and a position of the guide unit has to be moved according to a size of the sheets. Thus, there is a problem in that a mechanism and control are complicated and manufacturing cost increases.